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Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. [2] In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). [3] It is composed of hematopoietic cells, marrow adipose tissue, and supportive stromal cells.
Extremely small vessels located within bone marrow, the spleen and the liver. They are roughly grouped as "arterial" and "venous", determined by whether the blood in it is flowing away from (arterial) or toward (venous) the heart .
The nutrient artery (arteria nutricia, or central artery), usually accompanied by one or two nutrient veins, enters the bone through the nutrient foramen, runs obliquely through the cortex, sends branches upward and downward to the bone marrow, which ramify in the endosteum–the vascular membrane lining the medullary cavity–and give twigs to the adjoining canals.
When bone marrow develops, it eventually assumes the task of forming most of the blood cells for the entire organism. [3] However, maturation, activation, and some proliferation of lymphoid cells occurs in the spleen, thymus, and lymph nodes. In children, haematopoiesis occurs in the marrow of the long bones such as the femur and tibia.
The red bone marrow is derived from the layer of the embryo called the mesoderm. Haematopoiesis is the process by which all mature blood cells are produced. It must balance enormous production needs (the average person produces more than 500 billion blood cells every day) with the need to regulate the number of each blood cell type in the ...
Trabecular marrow is composed of a network of rod- and plate-like elements that make the overall organ lighter and allow room for blood vessels and marrow. Trabecular bone accounts for the remaining 20% of total bone mass but has nearly ten times the surface area of compact bone.
Cellular factors include reduced number and function of bone-marrow derived endothelial progenitor cells. [25] and reduced ability of those cells to form blood vessels. [26] Formation of additional capillaries and larger blood vessels (angiogenesis) is a major mechanism by which a cancer may help to enhance its own growth.
CEPs are derived from EPCs within the bone marrow, and the bone marrow is a reservoir of stem and progenitor cells. These cell types accelerate the healing process and prevent further complications such as hypoxia by gathering the cellular materials to reconstruct the endothelium.